import { Capacitor } from '@capacitor/core'

function csvCell(v: string | number | null | undefined): string {
  const s = v == null ? '' : String(v)
  return '"' + s.replace(/"/g, '""') + '"'
}

// 导出 UTF-8 BOM 的 CSV，Excel 可直接打开中文不乱码；返回落盘位置（原生平台）
export async function downloadCsv(filename: string, rows: (string | number | null | undefined)[][]): Promise<string> {
  const content = rows.map(r => r.map(csvCell).join(',')).join('\r\n')
  const text = '\ufeff' + content
  if (Capacitor.isNativePlatform()) {
    const { downloadText } = await import('./download')
    return downloadText(filename, text)
  }
  const blob = new Blob([text], { type: 'text/csv;charset=utf-8' })
  const url = URL.createObjectURL(blob)
  const a = document.createElement('a')
  a.href = url
  a.download = filename
  a.click()
  window.setTimeout(() => URL.revokeObjectURL(url), 10000)
  return ''
}